This invention is directed to a liquid-vapor separator structure wherein surface tension forces are employed to separate liquid from the vapor and is particularly useful in near-zero gravity environment.
Spinning or accelerating a spacecraft provides the force to separate the liquid from the gas or vapor in the propellant tanks. However, when a non-spinning body is in free fall, some means must be employed to cause the liquid to be delivered to that it is available for use without also allowing the pressurizing gas to exit from the tank. Mechanical devices such as pistons, bladders, metallic bellows, elastomeric diaphragms, metallic diaphragms and rolling diaphragms have each been considered and tested. Each has advantages and disadvantages but the problems they now present in weight and reliability require further investigation and development. Whenever there is a moving part, as in each of the above listed systems, reliability is reduced.
As a result of that, capillary separation systems have been contemplated. The use of surface tension as a separation method in acceleration fields less than 10.sup.-4 g has previously been accomplished by devices utilizing fine mesh, double dutch twill screen. The surface tension forces resulting from micron size small openings in the screen have been utilized to provide liquid communication through the screen while preventing the passage of gas through the screen. In double dutch twill woven screen each shute wire passes successively over two and under two warp wires. The shute wires are driven up close and deformed so that the mesh count is in excess of twice the sum of the wire count. The resultant port openings are of triangular shape and no through openings are visible except when the screen wire is viewed at an angle. The shute wires and warp wires are on the order of 0.001 inches in diameter and the finished woven wire screens have a 10 micron pore. Such a screen does not have sufficient structural integrity to be used alone, and must be supported. Also, careful handling is required to prevent bending and stretching because opening of the pores reduces the differential pressure that can be supported. Devices using this fine mesh screen concept are described in an article entitled, "A Survey of Current Development in Surface Tension Devices for Propellant Acquisition" by S. C. DeBrock et al. in Journal of Spacecraft and Rockets, Vol. 8, No. 2, February 1971, pgs. 83-98.
Thus, a new concept is required to provide a reliable propellant management device for a spacecraft which is to operate in a very low omnidirectional gravity field and therefore needs a suitable propellant management device to provide gas-free propellant.